This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2001-000192, filed Jan. 4, 2001, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a whole-screen distance measurement apparatus in which a distance measurement area is set also in a peripheral region outside a region to be photographed, particularly to a distance measurement apparatus of a camera in which erroneous distance measurement with respect to miscellaneous subjects (non-major subjects) is eliminated and a major subject is detected exactly.
2. Description of the Related Art
Various techniques concerning a multi-point distance measurement apparatus of a camera have heretofore been proposed. The multi-point distance measurement apparatus has a technique of selecting one or a plurality of results from distance measurement results of a plurality of distance measurement areas disposed in a region to be photographed, and detecting a major subject as a final distance measurement result.
When the number of distance measurement areas increases, it is important to select a distance measurement area with the major subject existing therein from these areas. For detection of the major subject by the conventional proposed techniques, a closest distance selection has been the mainstream in which a subject existing in the vicinity of the camera is regarded as the major subject, and a shortest distance output is selected from obtained distance measurement results of all distance measurement areas. For example, for a souvenir picture when sightseeing, a person as the major subject exists in a position closest to the camera in the region to be photographed. In such a general photography scene, the closest distance selection has been a very effective technique of major subject detection.
However, there are various patterns in the photography scene in accordance with a photographer""s intention. When an attempt is made to exactly detect the major subject in any photography scene, many photography scenes cannot be handled by the closest distance selection alone.
To solve the problem, a large number of variously improved techniques of closest distance selection have also been proposed. Techniques such as center-oriented closest distance selection for performing weighting so that priority is given to the center of a photography screen during the closest distance selection are also known.
In a photography scene such as a full-length portrait in which a person is photographed to the vicinity of the feet, ground in the vicinity of the person""s feet is closest to the camera, and is judged as an area in which the major subject exists. Therefore, a photograph in which the vicinity of the feet is focused and the person""s face is out of focus is taken. On the other hand, when priority is given to the center of the photography screen, the vicinity of the feet can be prevented from being focused to some degree.
When the whole-screen distance measurement apparatus is used, in addition to major subject detection, a technique for excluding miscellaneous subjects (indicating subjects other than the major subject herein) is important. In other words, the major subject cannot appropriately be detected without the technique of excluding the miscellaneous subjects.
However, the conventional proposed techniques do not extend to the technique of excluding the miscellaneous subjects in the whole-screen distance measurement apparatus. That is, in the conventional multi-point distance measurement apparatus, the closest distance selection is performed in various methods, but an optimum major subject is not necessarily detected. As described above, depending upon the photography scene, the problem that the miscellaneous subjects are focused, and the major subject is out of focus is not solved.
An object of the present invention is to provide a distance measurement apparatus of a camera which exactly excludes miscellaneous subjects from a photography scene, and quickly realizes detection of an optimum major subject.
According to the present invention, there is provided a distance measurement apparatus of a camera including: distance measurement means having a plurality of distance measurement areas in a region to be photographed by the camera and a peripheral region of the region to be photographed; classification means for grouping one or more distance measurement areas whose distance measurement outputs in difference between any two adjacent distance measurement areas are in a predetermined range and which are adjacent to one another in the plurality of distance measurement areas into a single distance measurement area group; exclusion means for excluding the distance measurement area which belongs to a group extending over the region to be photographed and the peripheral region among the groups classified by the classification means; and selection means for selecting the distance measurement area indicating a closest distance and selecting the distance measurement output of the selected distance measurement area as a final distance measurement output among the distance measurement outputs of the distance measurement areas which are not excluded by the exclusion means in the region to be photographed.
Furthermore, the distance measurement apparatus of the camera has the following distance measurement steps: a step of performing a distance measurement operation with respect to a plurality of distance measurement areas disposed in a region to be photographed by the camera and a peripheral region of the region to be photographed; a step of dividing distance measurement outputs of the plurality of distance measurement areas into groups; a step of excluding the distance measurement area which belongs to a group extending over the region to be photographed and the peripheral region in the classified groups; and a step of selecting the distance measurement output suitable for predetermined conditions as a final distance measurement output from the distance measurement outputs of the distance measurement areas which are not excluded by the exclusion step in the region to be photographed.
The distance measurement apparatus of the camera constituted as described above obtains subject distance information (or a phase difference of a subject luminance signal) of each distance measurement area by a two-dimensional photoelectric conversion means in which a plurality of distance measurement areas including a peripheral region outside a region to be photographed are disposed, groups the distance measurement areas whose numeric values are in a predetermined range and which are adjacent to one another from the obtained subject distance information, excludes the groups extending into the region to be photographed, performs a distance measurement operation processing of the major subject by the distance measurement results of the groups existing only in the region to be photographed, and selects a shortest distance as the final distance measurement output from the distance measurement results.